Cold - Water Injection into Single - and Two - Phase Geothermal Reservoirs

Numerical simulation techniques have been employed by several suthors (see e.g. Benson and Approximate analytical solutions a rived for Bodvarsson, 1982; Garg and Pritchett, 1384 to cold water injection into single0-phase “porous medium” geothermal reservoirs. A (liquid) and two-phase (liquid water/steam) numerical geothermal reservoir simulator is used “porous medium” reservoirs. Injection of cold to verify the applicability of the analytical water into a geothermal reservoir results in the solutions for pressure transient analysis. In outward propagation of a cold front of which the accordance with these numerical results, the radius increases in proportion to the square root analytical solutions indicate that the pressure of time; during the subsequental fall-off phase, buildup behavior during injection into either a the cold front is more or less stationary. In single-phase-liquid or two-phase reservoir is two-phase reservoirs, a condensation front moves governed by the kinematic viscosity of the cold ahead of the cold front; the radius of the injected fluid. The fall-off pressures after cold condensation front also increases with the square water injection into a single-phase liquid reservoir root of time, but, unlike the cold front, the (except for very early shutin times) are primarily condensation front does not remain stationary controlled by the kinematic visc during the fall-off phase. in situ (hot) reservoir fluid. Fo reservoirs, however, the fall-off results (Garg and Pritchctt, 1984) considerably more complex and cannot be fully pressure buildup data from both described by the analytical solution developed in d two-phase reservoi rs can be this paper. y the semi-log method provided that the fluid properties (viscosity, density) of the INTRODUCTION cold iqiected fluid are used. Fluid properties for the in ritu hot water are required to interpret Traditionally, cold-wa ing of pressure fall-off a after injection into single geothermal wells takes place shortly after the phase reservoirs Fall-off data for two-phase well is completed. Cold water is injected into reservoirs, however, exhibit ra ther complex investigate cold-water injection into single-p h ase